Photosensitive elements obtained by using a photosensitive resin composition layer along with a support and protective film have been widely used in the prior art as resist materials used in etching treatment or plating treatment in the production of printed wiring boards.
Printed wiring boards are produced by a method consisting of, for example, laminating a photosensitive element onto a copper-clad laminated substrate, exposing a pattern and removing the portion other than the exposed portion with a developing solution, followed by forming a pattern by carrying out etching treatment or plating treatment and separating and removing the cured portion from the substrate.
Mercury lamps have mainly been used for the light source for pattern exposure. However, since the light from a mercury lamp contains ultraviolet rays (light having a wavelength of 400 nm or less) that are harmful to the human body, it had problems in terms of work safety. Although there are also exposure methods that use a visible light laser for the light source, this method requires the use of a resist that is sensitive to visible light, and these resists have limitations on the environment in which exposure can be carried out, such as having to be handled in a darkroom or under a red lamp.
In consideration of the above, light from which 99.0% or more of the light having a wavelength of 365 mm or less from a light source, such as that from a mercury lamp light source is cut off using a filter has come to be used for pattern exposure. In addition, gallium nitride-based blue laser light sources, which generate light having a wavelength of 400 to 415 nm and have a long service life and high output, have come to be able to be acquired inexpensively in recent years, and these are also used as light sources for pattern exposure.
Moreover, a method has recently been proposed in which exposure is carried out using a direct writing method in which the exposure light is in the form of an image by arranging a plurality of mirrors and changing the angle of each mirror as necessary (see, for example, Non-Patent Document 1). In this exposure device as well, light from which 99.5% or more of the light having a wavelength of 365 nm or less from a mercury lamp light source is cut off by using a filter or a gallium nitride-based semiconductor laser light source may be used. [Non-Patent Document 1] Electronics Mounting Technology, June 2002 Edition (p. 74-79)